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Peptidyl post-translational modifications (PTMs) could influence the final quality of processed meat. In this study, the peptide oxidative phenomena in Spanish dry-cured ham (Biceps femoris muscle) was evaluated at different ripening times (9, 12, 15, 18 and 24 months of processing) evidencing interactions amongst the lipid and protein oxidation, major peptidyl PTMs and the release of free amino acids (FAAs). Results showed that 12 months of processing enabled the most abundant protein-bound carbonyls, while TBARS value was significantly favored (p < 0.001) by ripening. However, FAAs were still intensively generated during overall ripening. Peptidomics and chemometrics further revealed that proteolysis mostly hampered the oxidized peptides rather than the deamidated ones during ripening. Myosin light chain (MYL1 and MYL3) showed high oxidative susceptibility owing to peptidyl methionine and proline oxidation as well as acetaldehyde adduct formation on lysine or histidine residues., Grant AGL2017-89381-R and FEDER funds from the Spanish Ministry of Economy, Industry and Competitiveness, and Ramón y Cajal postdoctoral contract by L.M. are acknowledged. C.L. appreciated the financial support from China Scholarship Council (CSC) through the State Scholarship Fund for Overseas Study (No. 201806760050). The peptidomic analysis was performed in the proteomics facility of SCSIE University of Valencia. This proteomics laboratory is a member of Proteored, PRB3 and is supported by grant PT17/0019, of the PE I + D + i 2013-2016, funded by ISCIII and ERDF

The aim of this work was to quantify changes in the abundance of the major sarcoplasmic proteins throughout the ham dry-curing process by using a label-free mass spectrometry methodology based on the measurement of mass spectral peak intensities obtained from the extracted ion chromatogram. For this purpose, extraction of sarcoplasmic proteins was followed by trypsin digestion and analysis by nanoliquid chromatography coupled to tandem mass spectrometry (Q/TOF) for the identification and relative quantification of sarcoplasmic proteins through individual quantification of trypsinised peptides. In total, 20 proteins, including 12 glycolytic enzymes, were identified and quantified. The accuracy of the protocol was based on MS/MS replicates, and beta-lactoglobulin protein was used to normalise data and correct possible variations during sample preparation or LC-MS/MS analysis. Mass spectrometry-based proteomics provides precise identification and quantification of proteins in comparison with traditional methodologies based on gel electrophoresis, especially in the case of overlapping proteins. Moreover, the label-free approach used in this study proved to be a simple, fast, reliable method for evaluating proteolytic degradation of sarcoplasmic proteins during the processing of dry-cured ham.

Recent advances in proteomics have become an indispensable tool for a fast, precise and sensitive analysis of proteins in complex biological samples at both, qualitative and quantitative level. In this study, a label-free quantitative proteomic methodology has been optimised for the relative quantitation of proteins extracted from raw pork meat. So, after the separation of proteins by one-dimensional gel electrophoresis and trypsin digestion, their identification and quantitation have been done using nanoliquid chromatography coupled to a quadrupole/time-of-flight (Q/ToF) mass spectrometer. Relative quantitation has been based on the measurement of mass spectral peak intensities, which have been described that are correlated with protein abundances. The results obtained regarding linearity, robustness, repeatability and accuracy show that this procedure could be used as a fast, simple, and reliable method to quantify changes in protein abundance in meat samples., The research leading to these results received funding from the European Union 7th Framework Programme (FP7/2007-2013) under Grant Agreement 312090 (BACCHUS). This publication reflects only the author views and the Community is not liable for any use made of the information contained therein. JAEDOC-CSIC postdoctoral contract to L.M. is also acknowledged. FPI Scholarship BES-2011-046096 and grant AGL2010-16305 from MINECO (Spain) and FEDER funds are also acknowledged.

The complex proteolysis in Spanish dry-cured ham processing generates large amounts of small peptides and free amino acids which are responsible for the characteristic texture and flavour of this traditional product. The aim of this work was to study the degradation of the giant protein titin throughout the dry-curing process (2, 3.5, 5, 6.5, and 9 months) through the use of proteomic tools. A total of 320 peptides have been identified by nanoliquid chromatography coupled to tandem mass spectrometry, being some of them identified only at 9 months of processing. In order to confirm the absence of these peptides at other times of processing, MALDI-TOF MS was also employed as a fast and easier technique. Only four peptides, KDEAAKPKGPIKGVAKK, KKLRPGSGGEK, KNTDKWSECAR and ISIDEGKVL, were exclusively identified at 9 months of curing by using both methodologies so that these peptides could be used as potential biomarkers of dry-cured ham processing time., FPI Scholarship BES-2011-046096 from MINECO (Spain) to M.G. and grant AGL2010-16305 from MINECO and FEDER funds are fully acknowledged. JAEDOC-CSIC postdoctoral contract to L.M. is also acknowledged. The proteomic analysis was carried out in the SCSIE_University of Valencia Proteomics Unit, a member of ISCIII ProteoRed Proteomics Platform.

Pork meat is generally recognised as a food with relevant nutritional properties because of its content in high biological value proteins, group B vitamins, minerals especially heme iron, trace elements and other bioactive compounds. But pork meat also contributes to the intake of fat, saturated fatty acids, cholesterol, and other substances that, in inappropriate amounts, may result in negative physiologically effects. However, there are relevant factors affecting the content of many of these substances and somehow such variability should be taken into consideration. So, genetics, age and even type of muscle have a relevant influence on the amount of fat and the contents in heme iron. Also the composition in fatty acids of triacylglycerols is very sensitive to the contents of cereals in the feed; for instance, polyunsaturated fatty acids may range from 10% to 22% in pork meat. The content of other nutrients, like vitamins E and A, are also depending on the type of feed. Some bioactive substances like coenzyme Q10, taurine, glutamine, creatine, creatinine, carnosine and anserine show a large dependence on the type of muscle. This manuscript describes the main factors affecting the composition of pork meat nutrients and how these changes may affect the general food composition databases. (C) 2012 Elsevier Ltd. All rights reserved., Grant AGL2010-16305 from the Spanish Ministry of Science and Innovation (Madrid, Spain) and FEDER Funds and collaboration of Vaquero Foundation for R+D on Pork Meat (Madrid, Spain) are acknowledged. Grant PROMETEO/2012/001 from Generalitat Valenciana (Spain) is also acknowldeged. Work prepared within the Unidad Asociada IAD (UPV)-IATA (CSIC) framework.

The effect of partial replacement of NaCl by KCl in the dry-curing of loins has been evaluated by biochemical and sensory analysis of the final products. Endoproteolytic enzymes like cathpesins B and B + L appeared to be more active when more KCl and less NaCl were present in the curing salt while cathepsin H remained unaffected. Proteolysis was reflected by SDS–PAGE in the higher density of the sarcoplasmic proteins bands within the range 55.0–28.0 kDa. Alanyl aminopeptidase (AAP) was unaffected while arginyl and leucyl aminopeptidases were more activated by KCl. On the other hand, methionyl aminopeptidase and dipeptidylpeptidase I and III were more inhibited as KCl increased in the curing salt blends. The sensory analysis revealed no significant differences between control loins with 100% NaCl and those with up to 50% of KCl substitution. Furthermore, loins elaborated with 50% of each salt obtained the highest scores.

A porcine kidney enzyme extract containing high levels of cathepsins B and L activities has been successfully immobilised onto porous glass beads. Cathepsins showed improved stability when immobilised, exhibiting a half-life of 97.5 h at 30 °C vs 5.6 h for the free enzyme in solution. Immobilised reactors were incubated at 30 °C and fed with a 0.2% casein solution at pH 6.0. κ-casein was rapidly hydrolysed and almost fully degraded at 24 h while the degradation of α-casein and β-casein was achieved in 24–48 h. Polypeptides of M.W. 11, 19.5 and 32 kDa were generated and further degraded, while others (18 and 21 kDa) remained undegraded. Hydrolysis was much higher than that observed with the free enzymes. A substantial number of peptides with cut-off

A simple methodology, consisting in cation exchange HPLC separation combined with OPA postcolumn detection, has been succesfully applied to the analysis and detection of histidine dipeptides in feeds. The use of the proposed methodology, which is very simple and relatively fast, allows the detection of 2.63 ppm and 0.58 ppm of carnosine and anserine, respectively, in cattle feed. As balenine (3-methylhistidine) was not commercialy available, it was isolated from pork muscle and used as standard for its quantitation in feeds. These dipeptides have shown good stability against intense heat treatments, even at temperatures as high as 120 °C for 20 min. So, these histidine dipeptides can be feasible used as markers of animal protein content in feeds.

Muscle proteins, peptides and free amino acids were analysed at 2 h post-mortem as potential markers of different pork meat qualities. The meat quality classification was based on the measurements: pH2h, pH24h, the colour parameter L, and drip loss. The measurement of proteolytic fragments by SDS-PAGE revealed that the nebulin band was different among classes being more defined in the dark, firm and dry meat class. The detection and characterisation of small peptide fragments resulting from protein breakdown was done by isolation through cationic and reverse-phase chromatography. The analysis of peptide fractions isolated by reverse-phase chromatography revealed that could be used as potential markers of meat quality. So, peptide fraction 1 could be used to distinguish exudative from non-exudative meats and peptide fraction 4 distinguished dark, firm and dry meat from the rest. The concentration of free amino acids present in muscle was not different among qualities, probably due to the early post-mortem time (2 h) used in the study.

Freshness in one of the main quality attributes for fish commercialization and consumption. The traditional method for fish freshness evaluation is sensory analysis. However, instrumental methods such as electrical, texture and colour measurements, image analysis, VIS spectroscopy and electronic noses have been widely studied as objective alternatives. Each of these methods has advantages and disadvantages, but none of them can be universally proposed for defining and measuring fish freshness. This work evaluated the correlation of potentiometric measurements, obtained with gold and silver electrodes, with physicochemical, microbiological and biochemical analyses of sea bream stored under refrigeration. Results showed a strong correlation of the potentiometric measurements with the determined changes in fish, and an important correlation with the K1 index, dependent on the nucleoside degradation, which is used as a good indicator of post-mortem time and freshness.